Traditional surgical brain retractors are thin, firm or malleable bands of steel or other metal alloys, with abrupt or well-defined edges and have limited surface areas. The common structural form of the standard retractors is a simple strip of metal consisting of a metal strip which can be bent by hand and the surface of which typically is used to pull apart or spread delicate tissue. The strip typically is clearly outlined on the brain after a few minutes, and particularly noticeable are the pressure marks from the lateral spatula edges which indicate a high local compression stress. These traditional retractors can be introduced into the tissue of the brain or along brain surfaces, and then pulled with force to either separate or elevate the brain tissue during surgery. This method allows the target area to be illuminated and visualized in order to perform the surgical procedure. However, brain tissue is quite soft and delicate, particularly after trauma, loss of blood supply, or in the presence of brain edema. The brain tissue is a gel-like substance that can be easily damaged, and a complication known as “retraction injury” can occur, sometimes resulting in compromised brain function. The brain tissues can be torn by the relatively sharp edges of these retractors, and/or the retracted brain can lose blood supply when the local pressure beneath the retractor is greater than venous pressure. The result can be ischemic changes in the underlying brain and/or the more serious complication of venous brain infarction.
The combination factors including the softness of the brain tissue, and the effects of sharp, blunt edges and limited surface area of traditional metal band retractor also results in limited visualization of the surgical target area. The brain tends to extend beyond or “droop” around the edges of the retractor, limiting the area necessary for lighting and reducing overall visibility.
Furthermore, the amount of local pressure exerted by the retractor on the brain tissue must be limited to avoid injury, which may impede the surgeon's ability to safely gain enough visualization area. Oftentimes, the surgeon will resort to the strategy of exposing far more of the brain tissue than is necessary or desirable to open the area around the brain widely enough so as to limit the amount of local retraction pressure. This method is undesirable, as compared to a less invasive approach, for both the patient and surgeon.
It would be advantageous to provide a surgical instrument assembly that safely addresses the shortcomings of the presently-known instruments.